Buggy code:
private final LoggingAdapter log ; private final String authorization ; private final String restLocation ; private final String serviceLocation ; private final FutureUtils f ; private final AsyncHttpClient asyncHttpClient ; public DefaultGeoServerRest ( FutureUtils f , LoggingAdapter log , String serviceLocation , String user , String password ) throws Exception { } private CompletableFuture < Optional < Document > > get ( String path ) { } private CompletableFuture < Optional < Document > > get ( String path , boolean appendSuffix , boolean namespaceAware ) { } private CompletableFuture < Void > delete ( String path ) { } private CompletableFuture < Void > put ( String path , byte [ ] document ) { } private CompletableFuture < Void > put ( String path , byte [ ] document , String contentType ) { } private CompletableFuture < Void > post ( String path , byte [ ] document ) { } private CompletableFuture < Void > post ( String path , byte [ ] document , String contentType ) { } private String getServiceSettingsPath ( Workspace workspace , ServiceType serviceType ) { } @ Override public CompletableFuture < Void > putServiceSettings ( Workspace workspace , ServiceType serviceType , ServiceSettings serviceSettings ) { } @ Override public CompletableFuture < Void > postWorkspace ( Workspace workspace ) { } private < T > CompletableFuture < T > failure ( Exception e ) { } private String getWorkspacePath ( String workspaceId ) { } private String getWorkspacePath ( Workspace workspace ) { } private String getWorkspacesPath ( ) { } @ Override public CompletableFuture < List < Workspace > > getWorkspaces ( ) { } @ Override public CompletableFuture < Optional < DataStore > > getDataStore ( Workspace workspace , String dataStoreName ) { } private String getDataStorePath ( Workspace workspace , String dataStoreName ) { } private < T > T optionalPresent ( Optional < T > optional ) { } @ Override public CompletableFuture < List < DataStore > > getDataStores ( Workspace workspace ) { } @ Override public CompletableFuture < Void > postDataStore ( Workspace workspace , DataStore dataStore ) { } private String getDataStoresPath ( Workspace workspace ) { } private String getFeatureTypePath ( Workspace workspace , DataStore dataStore , FeatureType featureType ) { } private String getFeatureTypePath ( Workspace workspace , DataStore dataStore , String featureTypeName ) { } private CompletableFuture < Optional < FeatureType > > getFeatureType ( Workspace workspace , DataStore dataStore , String featureTypeName ) { } @ Override public CompletableFuture < List < FeatureType > > getFeatureTypes ( Workspace workspace , DataStore dataStore ) { } @ Override public CompletableFuture < Void > putFeatureType ( Workspace workspace , DataStore dataStore , FeatureType featureType ) { } private byte [ ] getFeatureTypeDocument ( FeatureType featureType ) throws IOException , XMLStreamException { } @ Override public CompletableFuture < Void > postFeatureType ( Workspace workspace , DataStore dataStore , FeatureType featureType ) { } private String getFeatureTypesPath ( Workspace workspace , DataStore dataStore ) { } @ Override public void close ( ) throws IOException { } private String getLayerGroupPath ( Workspace workspace , LayerGroup layerGroup ) { } private String getLayerGroupPath ( Workspace workspace , String layerGroupName ) { } private CompletableFuture < Optional < LayerGroup > > getLayerGroup ( Workspace workspace , String layerGroupName ) { } private String getLayerGroupsPath ( Workspace workspace ) { } @ Override public CompletableFuture < List < LayerGroup > > getLayerGroups ( Workspace workspace ) { } @ Override public CompletableFuture < Void > putLayerGroup ( Workspace workspace , LayerGroup layerGroup ) { } @ Override public CompletableFuture < Void > postLayerGroup ( Workspace workspace , LayerGroup layerGroup ) { } private byte [ ] getLayerGroupDocument ( Workspace workspace , LayerGroup layerGroup ) throws IOException , FactoryConfigurationError , XMLStreamException { } @ Override public CompletableFuture < Void > deleteDataStore ( Workspace workspace , DataStore dataStore ) { } @ Override public CompletableFuture < Void > deleteFeatureType ( Workspace workspace , DataStore dataStore , FeatureType featureType ) { } @ Override public CompletableFuture < Void > deleteLayerGroup ( Workspace workspace , LayerGroup layerGroup ) { } @ Override public CompletableFuture < Void > deleteWorkspace ( Workspace workspace ) { } private String getStringValue ( Node n ) { } @ Override public CompletableFuture < Optional < ServiceSettings > > getServiceSettings ( Workspace workspace , ServiceType serviceType ) { } private String getWorkspaceSettingsPath ( Workspace workspace ) { } @ Override public CompletableFuture < WorkspaceSettings > getWorkspaceSettings ( Workspace workspace ) { } @ Override public CompletableFuture < Void > putWorkspaceSettings ( Workspace workspace , WorkspaceSettings workspaceSettings ) { } @ Override public CompletableFuture < Optional < Workspace > > getWorkspace ( String workspaceId ) { } private String getStylePath ( String styleId ) { } private String getStylesPath ( ) { } @ Override public CompletableFuture < Optional < Style > > getStyle ( String styleId ) { } @ Override public CompletableFuture < List < Style > > getStyles ( ) { } @ Override public CompletableFuture < Void > postStyle ( Style style ) { } @ Override public CompletableFuture < Void > putStyle ( Style style ) { try { Document sld = style . getSld ( ) ; <START_BUG> return put ( ( ( ( getStylesPath ( ) ) + "?name=" ) + ( style . getStyleId ( ) ) ) , serialize ( sld ) , getStyleContentType ( sld ) ) ; <END_BUG> } catch ( Exception e ) { return failure ( e ) ; } } private String getStyleContentType ( Document sld ) { } private byte [ ] serialize ( Document sld ) throws TransformerConfigurationException , TransformerException , TransformerFactoryConfigurationError { } private Document parse ( InputStream is ) throws IOException , ParserConfigurationException , SAXException { } private Document parse ( InputStream is , boolean namespaceAware ) throws IOException , ParserConfigurationException , SAXException { } }

Fix:
return put ( getStylePath ( style . getStyleId ( ) ) , serialize ( sld ) , getStyleContentType ( sld ) ) ;